Recent studies on the mechanism of protein folding have indicated that proteins can exist as stable intermediate conformers that are structurally and energetically distinct from either native or denatured state. This ability of some proteins to accept an intermediate conformation with unique physical characteristics has an important biological significance, since it is clear that biological function(s) of all proteins are profoundly affected by their structure. Structural and energetical characteristics of human Growth Hormone were studied at pH range from 2.0 to 7.0, in presence or absence of ligands and denaturants. It is known that at low pH hGH has an intermediate state, that makes it to aggregate in solution. We studied this phenomena with the variety of methods, which include ITC, CD, HPLC, etc. Thermodynamic behavior of hGH leads to detailed description of its structural composition and to comprehension on molecular level of its biological role in living systems.